// specified in a function's 'gc' attribute. Algorithms are enabled by setting
// flags in a subclass's constructor, and some virtual methods can be
// overridden.
+//
+// GCStrategy is relevant for implementations using either gc.root or
+// gc.statepoint based lowering strategies, but is currently focused mostly on
+// options for gc.root. This will change over time.
//
-// When requested, the GCStrategy will be populated with data about each
-// function which uses it. Specifically:
+// When requested by a subclass of GCStrategy, the gc.root implementation will
+// populate GCModuleInfo and GCFunctionInfo with that about each Function in
+// the Module that opts in to garbage collection. Specifically:
//
// - Safe points
// Garbage collection is generally only possible at certain points in code.
// This information can used to emit the metadata tables which are required by
// the target garbage collector runtime.
//
+// When used with gc.statepoint, information about safepoint and roots can be
+// found in the binary StackMap section after code generation. Safepoint
+// placement is currently the responsibility of the frontend, though late
+// insertion support is planned. gc.statepoint does not currently support
+// custom stack map formats; such can be generated by parsing the standard
+// stack map section if desired.
+//
+// The read and write barrier support can be used with either implementation.
+//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_GCSTRATEGY_H
#define LLVM_CODEGEN_GCSTRATEGY_H
+#include "llvm/ADT/Optional.h"
#include "llvm/CodeGen/GCMetadata.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/Support/Registry.h"
#include <string>
namespace llvm {
-
- class GCStrategy;
-
- /// The GC strategy registry uses all the defaults from Registry.
- ///
- typedef Registry<GCStrategy> GCRegistry;
-
/// GCStrategy describes a garbage collector algorithm's code generation
/// requirements, and provides overridable hooks for those needs which cannot
- /// be abstractly described.
+ /// be abstractly described. GCStrategy objects currently must be looked up
+ /// through the GCModuleInfo analysis pass. They are owned by the analysis
+ /// pass and recreated every time that pass is invalidated.
class GCStrategy {
- public:
- typedef std::vector<GCFunctionInfo*> list_type;
- typedef list_type::iterator iterator;
-
private:
- friend class GCModuleInfo;
- const Module *M;
std::string Name;
-
- list_type Functions;
+ friend class GCModuleInfo;
protected:
+ bool UseStatepoints; /// Uses gc.statepoints as opposed to gc.roots,
+ /// if set, none of the other options can be
+ /// anything but their default values.
+
unsigned NeededSafePoints; ///< Bitmask of required safe points.
bool CustomReadBarriers; ///< Default is to insert loads.
bool CustomWriteBarriers; ///< Default is to insert stores.
bool CustomRoots; ///< Default is to pass through to backend.
- bool CustomSafePoints; ///< Default is to use NeededSafePoints
- ///< to find safe points.
bool InitRoots; ///< If set, roots are nulled during lowering.
bool UsesMetadata; ///< If set, backend must emit metadata tables.
public:
GCStrategy();
+ virtual ~GCStrategy() {}
- virtual ~GCStrategy();
-
-
- /// getName - The name of the GC strategy, for debugging.
- ///
+ /// Return the name of the GC strategy. This is the value of the collector
+ /// name string specified on functions which use this strategy.
const std::string &getName() const { return Name; }
- /// getModule - The module within which the GC strategy is operating.
- ///
- const Module &getModule() const { return *M; }
+ /// By default, write barriers are replaced with simple store
+ /// instructions. If true, then performCustomLowering must instead lower
+ /// them.
+ bool customWriteBarrier() const { return CustomWriteBarriers; }
+
+ /// By default, read barriers are replaced with simple load
+ /// instructions. If true, then performCustomLowering must instead lower
+ /// them.
+ bool customReadBarrier() const { return CustomReadBarriers; }
+
+ /// Returns true if this strategy is expecting the use of gc.statepoints,
+ /// and false otherwise.
+ bool useStatepoints() const { return UseStatepoints; }
+
+ /** @name Statepoint Specific Properties */
+ ///@{
- /// needsSafePoitns - True if safe points of any kind are required. By
- // default, none are recorded.
+ /// If the value specified can be reliably distinguished, returns true for
+ /// pointers to GC managed locations and false for pointers to non-GC
+ /// managed locations. Note a GCStrategy can always return 'None' (i.e. an
+ /// empty optional indicating it can't reliably distinguish.
+ virtual Optional<bool> isGCManagedPointer(const Value *V) const {
+ return None;
+ }
+ ///@}
+
+ /** @name GCRoot Specific Properties
+ * These properties and overrides only apply to collector strategies using
+ * GCRoot.
+ */
+ ///@{
+
+ /// True if safe points of any kind are required. By default, none are
+ /// recorded.
bool needsSafePoints() const {
- return CustomSafePoints || NeededSafePoints != 0;
+ return NeededSafePoints != 0;
}
- /// needsSafePoint(Kind) - True if the given kind of safe point is
- // required. By default, none are recorded.
+ /// True if the given kind of safe point is required. By default, none are
+ /// recorded.
bool needsSafePoint(GC::PointKind Kind) const {
return (NeededSafePoints & 1 << Kind) != 0;
}
-
- /// customWriteBarrier - By default, write barriers are replaced with simple
- /// store instructions. If true, then
- /// performCustomLowering must instead lower them.
- bool customWriteBarrier() const { return CustomWriteBarriers; }
-
- /// customReadBarrier - By default, read barriers are replaced with simple
- /// load instructions. If true, then
- /// performCustomLowering must instead lower them.
- bool customReadBarrier() const { return CustomReadBarriers; }
-
- /// customRoots - By default, roots are left for the code generator so it
- /// can generate a stack map. If true, then
- // performCustomLowering must delete them.
+
+ /// By default, roots are left for the code generator so it can generate a
+ /// stack map. If true, then performCustomLowering must delete them.
bool customRoots() const { return CustomRoots; }
- /// customSafePoints - By default, the GC analysis will find safe
- /// points according to NeededSafePoints. If true,
- /// then findCustomSafePoints must create them.
- bool customSafePoints() const { return CustomSafePoints; }
-
- /// initializeRoots - If set, gcroot intrinsics should initialize their
- // allocas to null before the first use. This is
- // necessary for most GCs and is enabled by default.
+ /// If set, gcroot intrinsics should initialize their allocas to null
+ /// before the first use. This is necessary for most GCs and is enabled by
+ /// default.
bool initializeRoots() const { return InitRoots; }
- /// usesMetadata - If set, appropriate metadata tables must be emitted by
- /// the back-end (assembler, JIT, or otherwise).
+ /// If set, appropriate metadata tables must be emitted by the back-end
+ /// (assembler, JIT, or otherwise). For statepoint, this method is
+ /// currently unsupported. The stackmap information can be found in the
+ /// StackMap section as described in the documentation.
bool usesMetadata() const { return UsesMetadata; }
-
- /// begin/end - Iterators for function metadata.
- ///
- iterator begin() { return Functions.begin(); }
- iterator end() { return Functions.end(); }
-
- /// insertFunctionMetadata - Creates metadata for a function.
- ///
- GCFunctionInfo *insertFunctionInfo(const Function &F);
+ ///@}
+
/// initializeCustomLowering/performCustomLowering - If any of the actions
/// are set to custom, performCustomLowering must be overriden to transform
/// the corresponding actions to LLVM IR. initializeCustomLowering is
/// optional to override. These are the only GCStrategy methods through
- /// which the LLVM IR can be modified.
- virtual bool initializeCustomLowering(Module &F);
- virtual bool performCustomLowering(Function &F);
- virtual bool findCustomSafePoints(GCFunctionInfo& FI, MachineFunction& MF);
+ /// which the LLVM IR can be modified. These methods apply mostly to
+ /// gc.root based implementations, but can be overriden to provide custom
+ /// barrier lowerings with gc.statepoint as well.
+ ///@{
+ virtual bool initializeCustomLowering(Module &F) {
+ // No changes made
+ return false;
+ }
+ virtual bool performCustomLowering(Function &F) {
+ llvm_unreachable("GCStrategy subclass specified a configuration which"
+ "requires a custom lowering without providing one");
+ }
};
-
+
+ /// Subclasses of GCStrategy are made available for use during compilation by
+ /// adding them to the global GCRegistry. This can done either within the
+ /// LLVM source tree or via a loadable plugin. An example registeration
+ /// would be:
+ /// static GCRegistry::Add<CustomGC> X("custom-name",
+ /// "my custom supper fancy gc strategy");
+ ///
+ /// Note that to use a custom GCMetadataPrinter w/gc.roots, you must also
+ /// register your GCMetadataPrinter subclass with the
+ /// GCMetadataPrinterRegistery as well.
+ typedef Registry<GCStrategy> GCRegistry;
}
#endif
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